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Flies share basic elements of human fear – but is it emotion?

FLIES seem to be chickens. They may look unfazed by our swatting, but they could in fact be rattled, a bit like us when we feel fear.

William Gibson of the California Institute of Technology in Pasadena and his colleagues exposed fruit flies to overhead shadows resembling aerial predators, such as birds, and found that the more shadows the flies saw, the more twitchy they got (Current Biology, doi.org/4nx).

The researchers also offered starved flies food, and part way through the meal threatened them with shadows. “The more shadows we used to disperse them from the food, the longer they took to ‘calm down’ and return to the food,” says co-author David Anderson, also at Caltech.

The researchers compare this to reactions of humans witnessing a shooting. The fear can outlast the gunshot itself, increasing if more shots are fired, and would arise whatever else the person was doing at the time of the shooting.